chi-square distribution: determining the constants c and d

If $X$ follows $\chi^2_5$, determine the constants $c$ and $d$ so that $P(c < X < d) = 0.95$ and $P(X < c) = 0.025$. $\chi^2$ is chi-squared distribution

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Hi, What have you tried? IMO you cannot find such values without using tables.. – TheJoker Nov 13 '12 at 3:55

1 Answer

the easiest way is to use R(qchisq). But I think you shoud do it yourself. Notice that chisq is the square sum of standard normal. $\chi_1^2=x^2, x \leadsto n(0,1)$. so in your case, it is $Y=\sum x_i, i=1,2,3,4,5$. where $Y$ has normal (0,5)

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chi-square with degree of 5. for P(X<c)=0.025 i got 0.831. But I am having trouble finding the d. Can I write P(X<d)-P(X<c)=0.95? – user48495 Nov 13 '12 at 5:45
oh i get it now. – user48495 Nov 13 '12 at 5:45